1. Field of the Invention
The present invention relates to a semiconductor device having a plurality of elements stacked and a method of manufacturing the same.
2. Description of the Related Art
Hitherto, in a semiconductor device for a use of an optical fiber, an optical disk, and the like, as part of an object of making the light output level of a semiconductor light emitting element assembled in the device constant, emission light of the light emitting element is detected by a light detecting mechanism. The light detecting mechanism may be constructed by, for example, a reflector that branches part of emission light and a light detecting element that detects the branched emission light. In the configuration, however, the number of parts increases and, moreover, a disadvantage occurs such that the reflector and the light detecting element have to be disposed with high precision with respect to the light emitting element. As one of measures solving such a disadvantage, the light emitting element and the light detecting element are integrally formed.
However, when the light emitting element and the light detecting element are formed integrally, there is the possibility that the light detecting element detects not only stimulated emission light to be inherently detected but also spontaneous emission light. In such a case, the light output level of the light emitting element measured on the basis of light detected by the light detecting element includes an error only by the amount of spontaneous emission light. Therefore, the method is also not suitable for uses necessitating high-precision control on the light output level.
Japanese Patent No. 2,877,785 discloses a technique of providing a control layer in a light detecting element and interrupting part of spontaneous emission light entering from a light emitting element before the light detecting element detects it.
The control layer is formed by oxidizing a part of the semiconductor material of the light detecting element. The reflectance of the oxidized semiconductor material is not so high, and the semiconductor material transmits some spontaneous emission light. It is therefore difficult to sufficiently lower the spontaneous emission light detection level of the light detecting element. There is consequently a disadvantage such that light detection precision is not sufficiently improved.